In this article, I will show How to extend the Operating System drive in Windows Server 2012?

Scenario

When I tried to Extend Volume for a specific drive in Windows Server 2012 R2 by opening:

Server Manager > Computer Management.

Disk Management > Right Click on C:\ Drive.

Although I have an unallocated free space (about 19.5 GB). But unfortunately, the Extend Volume option is grayed out as shown below.

Cause

The extend volume option is disabled because of there is no unallocated space beside directly the drive that you need to extend. and to be able to extend a specific drive volume you should make sure that there is no partition between the original partition and unallocated space as shown below

Solution

In this case, you will need to unallocated the drive space beside the operating system drive.(in my case it's F:\ ) but this means all data in this drive will be deleted! So, before we getting started you should Make sure that the unallocated space is at least equal to or greater than the used space in F:\ drive (the drive beside OS drive) to ensure that you can move the F:\ drive content to this space.

Steps

Create a new simple volume from the unallocated space.

Move the data files from F:\ Drive to the New Volume.

Delete F:\ Drive.

You are now having unallocated space beside the Operating System drive.

Again, try to extend the Operating System drive where the extend volume should be now enabled.

The Extend volume wizard should be started > Next.

By default, all free space will be set, you can change the amount of space based on your requirement.